This invention relates to overhead arm assemblies for supporting depending equipment and more particularly to arm assemblies for supporting and selectively locating such equipment relative to some associated body or member.
The invention is particularly applicable to use with medical ultrasonic diagnostic apparatus and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications in other fields which require exacting placement with each movement of some sensing apparatus or a work element. One such alternative application would be for use in conjunction with engraving apparatus.
In ultrasonic medical diagnostics, images of internal areas of a patient are obtained by transmitting ultrasonic energy into the patient and monitoring the ultrasonic echoes. A so-called planar slice of the patient is most commonly examined. The examination is typically accomplished by utilizing a single probe element which both transmits ultrasonic energy and receives the echoes. By monitoring the position and orientation of the probe as it is moved to various points along the line of intersection between the planar slice and the surface or body of the patient, signal processing equipment can transform the position data and echoes into a representation of the examined planar slice. An example of such processing equipment is shown in U.S. Pat. No. 3,036,390.
The ultrasonic probe is normally carried by an arm assembly defined by a plurality of moveable, jointed arms. These arms are constrained to movement within a single plane, i.e., the plane of the patient slice which is to be examined. Prior arm assemblies have generally comprised a plurality of pivotally interconnected arms such as is shown in U.S. Pat. No. 3,924,452, a plurality of linearly, slideably jointed arms such as is shown in U.S. Pat. No. 3,036,390 or a combination of these two arrangements. The designs of these and other prior arm assemblies have been such that there were problems in accurately selecting the plane of examination. Some prior assemblies were also lacking in adjustment flexibility and required movement of the patient for purposes of changing the plane of examination.
More particularly, and in practical application, doctors often wish to obtain and view more than one planar slice of a patient. These plural slices are most reliably diagnosed if they are parallel and spaced apart by known increments. In prior arm assemblies, especially those which required patient movement for changing the plane of examination, movement to parallel planes was usually arduous and imprecise. Even in the selection of an initial or first plane, alignment of the plane of interest in the patient and the scan plane of the arm was often haphazard and imprecise.
Another problem encountered with prior arm assemblies is that they have been awkward to operate. In some prior assemblies, the scan arms have not been counterweighted or if counterweighted, they have been done so in a crude and inaccurate manner. Often the arms have been constructed of lightweight materials and without proper counterweighting which required the operator to exert different amounts of force to produce the same scanning movement in different portions of the scan plane. This problem resulted in undesired degradation of the visual image being produced.
The present invention contemplates new and improved apparatus which overcomes all of the above referred to problems and others and provides an overhead arm and scanning assembly which is flexible, easy to use, and precisely oriented.